Description:
Anytime anyone tries to transfer a call to an external number outside the network the call drops immediately. The call drops using either attended transfer or blind transfer. All calls transfer successfully to other extensions within the network. However, calls transferred to an external number do transfer successfully if I wait for the phone I am calling to answer before I push the "Transfer" button to complete the transfer. I have been using the 3CX phone system for 17 months now. This just started happening about a week ago. I have made no changes to our firewall, nor have I made any changes to the 3CX server.
Failed Test Scenario:
1) A call is made to Phone A.
2) Phone A answers the call.
3) Phone A pushes the "Transfer" button on the screen. (I also tried pushing the hard transfer button on the phone)
4) Phone A dials phone B, which is an external number. (I have tried both 7 digit and 10 digit numbers)
5) Phone A pushes the "Send" button on the screen.
6) Phone A pushes the "Transfer" button on the screen again before phone B answers the call to complete the transfer.
7) The call is dropped immediately.
Successful Test Scenario:
1) A call is made to Phone A.
2) Phone A answers the call.
3) Phone A pushes the "Transfer" button on the screen.
4) Phone A dials phone B, which is a 7 or 10 digit external number.
5) Phone A pushes the "Send" button on the screen.
6) Phone A waits for phone B to answer.
7) After phone B answers the phone, phone A pushes the "Transfer" button on the screen again to complete the transfer.
8) The call is not dropped and is transferred successfully.
Note: The "Successful Test Scenario" shown above is the only way to get a transfer to work. However, most users on our network prefer to push the "Transfer" button twice before the other person picks up the phone as most users prefer not to talk to the other person unless it is necessary. It's basically a blind transfer but most users prefer to do it this way. Either way, it has always worked before. Besides, the blind transfer doesn't work anyway, which also has always worked before.
Failed Blind Transfer Scenario:
1) A call is made to Phone A.
2) Phone A answers the call.
3) Phone A pushes the "Transfer" button on the screen.
4) Phone A dials phone B, which is a 7 or 10 digit external number.
5) Phone A pushes the "Blind Transfer" button on the screen.
6) The call is dropped immediately.
Also, I am using two different SIP trunk providers. The other SIP trunk we have set up on our 3CX server works just fine with transferring calls. All calls transfer successfully using all the scenarios listed above on the other SIP trunk.
When I check the event log immediately after making a failed transfer, I get the following message:
Call or Registration to 9999999999@(Ln.10001@SIPTRUNK) has failed. 99.999.999.9 replied: 403 Forbidden; from IP:99.999.999.9:5060
SIP Server ID: 12294 06/23/2021 1:22:23 PM
I have extensively searched through Google and the 3CX forums for help with this problem and at least 99% of all the search results say to make sure that "Supports Re-Invite" and "Support Replaces" are unchecked in the SIP trunk "Options" tab. Unfortunately, they were already unchecked from the very beginning, so this was not a solution for me. Just out of curiosity, I checked or enabled the two options just to see what would happen and it still did not work, so I went back and unchecked or disabled the two options. Also, the "Support Re-Invites" and "Support 'Replaces' header" are both checked or enabled on all phone extensions in the "Options" tab.
One thing I noticed different about the two SIP trunks we have set up on our 3CX system is that when dialing an outside line from a phone using the SIP trunk with the failed transfers, the number on the caller ID has a +1 in front of the 10 digit number. When dialing an outside line from a phone using the SIP trunk with the successful transfers, the number only has a 1 in from of the 10 digit number. The + does not show up on the caller ID. So, I figured maybe this + has something to do with it. I tried everything I could to strip this plus from the caller ID by adding a "Source Pattern" in the SIP trunk settings "Caller ID". I tried countless combinations of settings as explained here. Nothing I tried would strip the + from the caller ID. After further researching, I learned that this + is probably controlled by our SIP trunk provider. I contacted them about it but they have not made any changes yet as they want me to try other things first including submitting this help with support and the 3CX forums which I'm doing now. I'm not sure if stripping the + from the caller ID would even fix the problem. But since I have no way of testing that right now, I don't know for sure.
I have also done tons of packet capturing while making these failed transfers using both Wireshark and Colasoft Capsa, but I could find no irregularities anywhere within the packet capture logs.
Our Current 3CX Setup:
All phones are Yealink T48s
Yealink firmware is 66.85.0.5
3CX Server product is Enterprise Annual, version 16.0.9
Number of Simultaneous Calls is 24
Number of G729 Channels is 24
Any help would be greatly appreciated.
Anytime anyone tries to transfer a call to an external number outside the network the call drops immediately. The call drops using either attended transfer or blind transfer. All calls transfer successfully to other extensions within the network. However, calls transferred to an external number do transfer successfully if I wait for the phone I am calling to answer before I push the "Transfer" button to complete the transfer. I have been using the 3CX phone system for 17 months now. This just started happening about a week ago. I have made no changes to our firewall, nor have I made any changes to the 3CX server.
Failed Test Scenario:
1) A call is made to Phone A.
2) Phone A answers the call.
3) Phone A pushes the "Transfer" button on the screen. (I also tried pushing the hard transfer button on the phone)
4) Phone A dials phone B, which is an external number. (I have tried both 7 digit and 10 digit numbers)
5) Phone A pushes the "Send" button on the screen.
6) Phone A pushes the "Transfer" button on the screen again before phone B answers the call to complete the transfer.
7) The call is dropped immediately.
Successful Test Scenario:
1) A call is made to Phone A.
2) Phone A answers the call.
3) Phone A pushes the "Transfer" button on the screen.
4) Phone A dials phone B, which is a 7 or 10 digit external number.
5) Phone A pushes the "Send" button on the screen.
6) Phone A waits for phone B to answer.
7) After phone B answers the phone, phone A pushes the "Transfer" button on the screen again to complete the transfer.
8) The call is not dropped and is transferred successfully.
Note: The "Successful Test Scenario" shown above is the only way to get a transfer to work. However, most users on our network prefer to push the "Transfer" button twice before the other person picks up the phone as most users prefer not to talk to the other person unless it is necessary. It's basically a blind transfer but most users prefer to do it this way. Either way, it has always worked before. Besides, the blind transfer doesn't work anyway, which also has always worked before.
Failed Blind Transfer Scenario:
1) A call is made to Phone A.
2) Phone A answers the call.
3) Phone A pushes the "Transfer" button on the screen.
4) Phone A dials phone B, which is a 7 or 10 digit external number.
5) Phone A pushes the "Blind Transfer" button on the screen.
6) The call is dropped immediately.
Also, I am using two different SIP trunk providers. The other SIP trunk we have set up on our 3CX server works just fine with transferring calls. All calls transfer successfully using all the scenarios listed above on the other SIP trunk.
When I check the event log immediately after making a failed transfer, I get the following message:
Call or Registration to 9999999999@(Ln.10001@SIPTRUNK) has failed. 99.999.999.9 replied: 403 Forbidden; from IP:99.999.999.9:5060
SIP Server ID: 12294 06/23/2021 1:22:23 PM
I have extensively searched through Google and the 3CX forums for help with this problem and at least 99% of all the search results say to make sure that "Supports Re-Invite" and "Support Replaces" are unchecked in the SIP trunk "Options" tab. Unfortunately, they were already unchecked from the very beginning, so this was not a solution for me. Just out of curiosity, I checked or enabled the two options just to see what would happen and it still did not work, so I went back and unchecked or disabled the two options. Also, the "Support Re-Invites" and "Support 'Replaces' header" are both checked or enabled on all phone extensions in the "Options" tab.
One thing I noticed different about the two SIP trunks we have set up on our 3CX system is that when dialing an outside line from a phone using the SIP trunk with the failed transfers, the number on the caller ID has a +1 in front of the 10 digit number. When dialing an outside line from a phone using the SIP trunk with the successful transfers, the number only has a 1 in from of the 10 digit number. The + does not show up on the caller ID. So, I figured maybe this + has something to do with it. I tried everything I could to strip this plus from the caller ID by adding a "Source Pattern" in the SIP trunk settings "Caller ID". I tried countless combinations of settings as explained here. Nothing I tried would strip the + from the caller ID. After further researching, I learned that this + is probably controlled by our SIP trunk provider. I contacted them about it but they have not made any changes yet as they want me to try other things first including submitting this help with support and the 3CX forums which I'm doing now. I'm not sure if stripping the + from the caller ID would even fix the problem. But since I have no way of testing that right now, I don't know for sure.
I have also done tons of packet capturing while making these failed transfers using both Wireshark and Colasoft Capsa, but I could find no irregularities anywhere within the packet capture logs.
Our Current 3CX Setup:
All phones are Yealink T48s
Yealink firmware is 66.85.0.5
3CX Server product is Enterprise Annual, version 16.0.9
Number of Simultaneous Calls is 24
Number of G729 Channels is 24
Any help would be greatly appreciated.
